1. Field of the Invention
The present invention relates to a molded article of monomer-cast nylon excellent in the antistatic properties.
2. Discussion of Background
A molded article of monomer-cast nylon can be obtained by polymerizing a monomer material such as .epsilon.-caprolactam in a mold.
Such a molded article of monomer-cast nylon is excellent in the mechanical properties and thus is useful for various mechanical parts such as gear wheels, wheels, rollers or screws.
However, the monomer-cast nylon has an electrical insulating property (its volume resistivity is from 10.sup.14 to 10.sup.15 .OMEGA.-cm). In its applications where static electricity is undesirable, it is desired to have antistatic properties imparted.
In order to impart antistatic properties to the monomer-cast nylon, it is conceivable to incorporate fine metal powder, metal fiber, carbon black or inorganic particles coated with a metal, to the monomer material. However, among such additives, the metal type has a problem that when a static mold method is employed as commonly employed in the case of usual monomer-casting, it tends to settle in the mold and can not uniformly be dispersed. In the case of carbon black, because of its large specific surface area, it adsorbs the monomer to form a paste. Therefore, it may be added only at a level of 5% by weight at best. Accordingly, its volume resistivity can be reduced only to a level of from 10.sup.10 to 10.sup.11 .OMEGA.-cm. Besides, the mechanical properties tend to be thereby impaired.